关系子句是一种附属子句,是由关系代名词who、which、that所标示的形容词子句,在句子里扮演修饰名词的角色,对相关的名词加以限定、形容、解释、说明,补充关于名词的讯息:
I met an old friend [who has five children].
→who子句用来限定前面的friend→who是子句内的主词
I bought a smartphone [which my friend recommended ______].
→which子句用来限定前面的smartphone→which是子句内的受词
这样的关系子句有一个特色,就是子句都少了一个名词,这个“失踪”的名词由关系代名词来“代替”,本尊则指向前面的名词:
I met a friend. The friend has five children.
⬆_______⬆
I met a friend [who has five children].
⬆____|
由于有一个“失踪人口”,关系子句和其他修饰名词的子句补语并不一样:
He told a story [that a frog turned into a prince].
→that子句用来说明前面的story,并非关系子句,因人物俱在
He was sad for the reason [that his girl friend left him].
→that子句用来说明前面的reason,并非关系子句,因人物齐全
——劉美君. (2012). 英文文法有道理! 重新認識英文文法觀念. 聯經.